colorspace: The color space in which color values are expressed. Quartz retains this object; upon return, you may safely release it.
startPoint: The starting point of the axis, in the shading's target coordinate space.
endPoint: The ending point of the axis, in the shading's target coordinate space.
function: A CGFunction object. This object refers to your function for creating an axial shading. Quartz retains this object; upon return, you may safely release it.
extendStart: A Boolean value that specifies whether to extend the shading beyond the starting point of the axis.
extendEnd: A Boolean value that specifies whether to extend the shading beyond the ending point of the axis.

Returns a new Quartz axial shading or nil on any error.

Discussion
An axial shading is a color blend that varies along a linear axis between two endpoints and extends indefinitely perpendicular to that axis. When you are ready to draw the shading, call the function CGContextMBS.DrawShading.

Function:
Creates a Quartz radial shading.Notes:
Parameters
colorspace: The color space in which color values are expressed.
startPoint: The center of the starting circle, in the shading's target coordinate space.
startRadius: The radius of the starting circle, in the shading's target coordinate space.
endPoint: The center of the ending circle, in the shading's target coordinate space.
endRadius: The radius of the ending circle, in the shading's target coordinate space.
function: A CGFunction object. This object refers to your function for creating a radial shading.
extendStart: A Boolean value that specifies whether to extend the shading beyond the starting circle.
extendEnd: A Boolean value that specifies whether to extend the shading beyond the ending circle.

Returns a new Quartz radial shading or nil on any error.

A radial shading is a color blend that varies between two circles. To draw the shading, call the function CGContextDrawShading.